a25a57f6ac
We cannot in general detect that truncation happened. At the moment we use a heuristic to compare the file size before and after a write happened. If the new file size is smaller than the old, we correctly handle truncation and dump the entire file to stdout. If it so happened that the new size is larger or equal to the old size after the file had been truncated without any reads in between, we will assume the data was appended to the file. There is no known way around this other than using inotify or kevent which is outside the scope of sbase.
135 lines
2.5 KiB
C
135 lines
2.5 KiB
C
/* See LICENSE file for copyright and license details. */
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#include <sys/stat.h>
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#include <limits.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "text.h"
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#include "util.h"
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static int fflag = 0;
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static void
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dropinit(FILE *fp, const char *str, size_t n)
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{
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char *buf = NULL;
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size_t size = 0, i = 0;
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ssize_t len;
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while (i < n && (len = getline(&buf, &size, fp)) != -1)
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if (len > 0 && buf[len - 1] == '\n')
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i++;
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free(buf);
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concat(fp, str, stdout, "<stdout>");
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}
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static void
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taketail(FILE *fp, const char *str, size_t n)
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{
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char **ring = NULL;
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size_t i, j, *size = NULL;
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ring = ecalloc(n, sizeof *ring);
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size = ecalloc(n, sizeof *size);
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for (i = j = 0; getline(&ring[i], &size[i], fp) != -1; )
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i = j = (i + 1) % n;
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if (ferror(fp))
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eprintf("%s: read error:", str);
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do {
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if (ring[j]) {
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fputs(ring[j], stdout);
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free(ring[j]);
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}
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} while ((j = (j + 1) % n) != i);
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free(ring);
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free(size);
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}
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static void
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usage(void)
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{
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eprintf("usage: %s [-f] [-n lines] [file ...]\n", argv0);
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}
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int
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main(int argc, char *argv[])
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{
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struct stat st1, st2;
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FILE *fp;
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size_t n = 10, tmpsize;
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int ret = 0, newline, many;
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char *lines, *tmp;
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void (*tail)(FILE *, const char *, size_t) = taketail;
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ARGBEGIN {
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case 'f':
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fflag = 1;
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break;
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case 'n':
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lines = EARGF(usage());
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n = estrtonum(lines, 0, MIN(LLONG_MAX, SIZE_MAX));
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if (lines[0] == '+')
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tail = dropinit;
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break;
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ARGNUM:
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n = ARGNUMF();
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break;
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default:
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usage();
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} ARGEND;
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if (argc == 0)
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tail(stdin, "<stdin>", n);
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else {
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if ((many = argc > 1) && fflag)
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usage();
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for (newline = 0; argc > 0; argc--, argv++) {
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if (!(fp = fopen(argv[0], "r"))) {
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weprintf("fopen %s:", argv[0]);
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ret = 1;
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continue;
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}
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if (many)
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printf("%s==> %s <==\n",
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newline ? "\n" : "", argv[0]);
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if (stat(argv[0], &st1) < 0)
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eprintf("stat %s:", argv[0]);
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newline = 1;
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tail(fp, argv[0], n);
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if (fflag && argc == 1) {
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tmp = NULL;
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tmpsize = 0;
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for(;;) {
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while (getline(&tmp, &tmpsize, fp) != -1) {
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fputs(tmp, stdout);
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fflush(stdout);
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}
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if (ferror(fp))
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eprintf("readline %s:", argv[0]);
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clearerr(fp);
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/* ignore error in case file was removed, we continue
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* tracking the existing open file descriptor */
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if (!stat(argv[0], &st2)) {
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if (st2.st_size < st1.st_size) {
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fprintf(stderr, "%s: file truncated\n", argv[0]);
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rewind(fp);
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}
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st1 = st2;
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}
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sleep(1);
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}
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}
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fclose(fp);
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}
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}
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return ret;
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}
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